Test chamber and method

ABSTRACT

A method for conditioning a fluid in a temperature-insulated test space and a test space of a test chamber for receiving test materials. A cascading cooling device creates a particular temperature range within the test space, and the cooling device has a first cooling circuit comprising a cascading heat exchanger, a first compressor, a condenser and a first expanding element, and a second cooling circuit comprising a heat exchanger, a second compressor, the cascading heat exchanger and a second expanding element. The cascading heat exchanger is cooled by the first cooling circuit, the heat exchanger is cooled by a bypass passing through the heat exchanger and bridging the cascading heat exchanger, the first compressor is turned off, and a first refrigerant is conducted and condensed in a gaseous state in the cascading heat exchanger on a low-pressure side of the bypass.

This application in a divisional of U.S. patent application Ser. No.16/444,167 filed on Jun. 18, 2019, which claims priority to EuropeanPatent Application No. 18178627.8 filed on Jun. 19, 2018, thedisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a method and a test chamber for conditioning afluid, particularly air, comprising a temperature-insulated test spacefor receiving test materials, said test space being sealable against anenvironment, a temperature ranging from −60° C. to +180° C. intemperature being realized within the test space by means of a cascadingcooling device of a temperature control device of the test chamber,having a first cooling circuit having a first refrigerant, a cascadingheat exchanger, a first compressor, a condenser and a first expandingelement, and having a second cooling circuit having a secondrefrigerant, a heat exchanger arranged in the test space, a secondcompressor, the cascading heat exchanger and a second expanding element,said cascading heat exchanger being cooled by the first cooling circuit.

BACKGROUND OF THE INVENTION

Such test chambers are commonly used for testing physical and/orchemical properties of objects, in particular devices. Therefore,temperature test chambers or climate test chambers are known withinwhich temperatures ranging from −60° C. to +180° C. can be set. Inclimate test chambers, desired climate conditions can be additionallyset to which the device or rather test materials will be exposed for adefined period of time. Such test chambers are regularly or partiallyrealized as a mobile apparatus which is connected to a building usingonly required supply lines and comprise all necessary structuralcomponents for controlling the temperature and conditioning. Atemperature of a test space, which receives the test materials to betested, is regularly controlled in an air circulation duct within thetest space. The air circulation duct forms an air treatment space in thetest space in which heat exchangers for heating or cooling the airflowing through the air circulation duct or the test space,respectively, are arranged. For this purpose, a fan or a ventilatorsuctions the air present in the test space and conducts it in the aircirculation duct to the corresponding heat exchangers or vice versa. Thetest materials can thus be controlled in temperature or even be exposedto a defined change in temperature. During a test interval, atemperature can repeatedly alternate between a temperature maximum and atemperature minimum of the test chamber, for example. Such a testchamber is known from EP 0 344 397 A1, for example.

Due to the high requirements for a temperature control within thetemperature range of the test chamber, fluctuations regularly occur in aload requirement while the test chamber is in operation. A refrigeratingcapacity generated by the corresponding compressor and expanding elementmust therefore be able to be adjusted continuously. Nevertheless, it isdesirable for the compressor, for example, to not be turned on and offtoo often in order to prolong a service life of the compressor. Thisrequirement is regularly solved by a tube section having anotheradjustable expanding element being formed between a high-pressure sideand a low-pressure side of a cooling circuit, a refrigerating capacitybeing able to be led back past the heat exchanger or cascading heatingexchanger to the corresponding compressor via the expanding element. Inthis needs-based distribution of a mass flow caused by the respectivecompressor in the corresponding cooling circuit, slight differences intemperature between an actual temperature and a set temperature can becompensated in the heat exchanger or the cascading heat exchanger,respectively, without having to result in disadvantageous loadingconditions in the corresponding compressors. In this context, however,it is disadvantageous for a compressor to always have to be in operationwhen there is a slight difference in temperature present in the heatexchanger, no matter how large the difference in temperature to becompensated by the cooling device is. The full refrigerating capacity ofthe compressor must be made available for a cooling requirement of only<1% of a total capacity, for example, in order to be able to maintainthe required set temperature in the heating exchanger. A majority of therefrigerating capacity is then led back to the corresponding compressorvia the tube section. Since continually turning the compressor on andoff is not possible and a fan has to be operated at the condenser alsoif need be, the cascading cooling device also consumes a comparativelylarge amount of energy for slight differences in temperature, which areto be compensated in the heat exchanger, using the known operatingmethod described above.

SUMMARY OF THE INVENTION

The object of the invention at hand is to propose a test chamber and amethod for conditioning air in a test space of a test chamber by meansof both of which the test chamber can be operated in an energy-efficientmanner.

The method for conditioning a fluid, particularly air according to theinvention comprises a temperature-insulated test space for receivingtest materials, said test space being sealable against an environment, atemperature ranging from −60° C. to +180° C. in temperature beingrealized within the test space by means of a cascading cooling device ofa temperature control device of the test chamber, having a first coolingcircuit having a first refrigerant, a cascading heat exchanger, a firstcompressor, a condenser and a first expanding element, and having asecond cooling circuit having a second refrigerant, a heat exchangerarranged in the test space, a second compressor, the cascading heatexchanger and a second expanding element, said cascading heat exchangerbeing cooled by the first cooling circuit, said heat exchanger beingsubsequently cooled by a bypass of the first cooling circuit by means ofthe first cooling circuit, said bypass passing through the heatexchanger and bridging the cascading heat exchanger, said firstcompressor being turned off, said first refrigerant being conducted andcondensed in a gaseous state in the cascading heat exchanger on alow-pressure side of the bypass.

In the method according to the invention, a temperature exchange with anenvironment of the test space is mostly prevented via a temperatureinsulation of side walls, bottom walls and top walls of the testchamber. The heat exchanger is connected to or is integrated in thesecond cooling circuit so that the second refrigerant circulating in thesecond cooling circuit flows through the heat exchanger. The heatexchanger of the second cooling circuit is arranged in the test space orrather in an air treatment space of the test space. Since the cascadingcooling device comprises two cascading cooling circuits, the secondcooling circuit is coupled to the first cooling circuit via thecascading heat exchanger in such a manner that the cascading heatexchanger serves as a condenser for the second cooling circuit. Thefirst and the second cooling circuit each comprise the first and thesecond compressor, respectively. In the first cooling circuit, thecondenser for the compressed first refrigerant is arranged in the flowdirection of the first refrigerant downstream of the first compactor.The compressed first refrigerant, which is highly-pressurized afterbeing compressed and is essentially gaseous, is condensed in thecondenser and is then available in an essentially liquid state. Theliquified first refrigerant continues to flow through the firstexpanding element, wherein it becomes gaseous again through expansiondue to a drop in pressure. Hence, the liquid first refrigerant flowsthrough the cascading heat exchanger which is cooled by this.

Subsequently, the gaseous first refrigerant is suctioned and compressedagain by the first compressor. The second cooling circuit is operatedcorresponding to the first cooling circuit, with the cascading heatexchanger serving as the condenser instead of using the condenser of thefirst cooling circuit in this instance, said cascading heat exchangeritself being cooled by the first cooling circuit. An expanding elementis understood to be at least an expansion valve, a throttle, throttlevalves or a different, suitable constriction of a fluid line.

In the invention at hand, it is intended to cool the heat exchanger bymeans of the bypass of the first cooling circuit passing through theheat exchanger and bridging the cascade heat exchanger. Depending on thetemperature requirements, the heat exchanger can then be cooled eithervia a combination of the first cooling circuit and the second coolingcircuit or only via the first cooling circuit. A refrigeration usingboth cooling circuits is intended if particularly low temperatures arenot to be attained, with the second compressor being able to be put outof operation in this instance. It becomes possible to save energy whenoperating the test space through this measure alone.

Since the cascading heat exchanger is basically always cooled when thefirst compressor is in operation, even if only a small refrigeratingcapacity is required in the heat exchanger, the first refrigerant orrather the mass flux of compressed refrigerant can be conducted throughthe cascading heat exchanger before redirecting the mass flow via a tubesection upstream of the compressor. Though the first refrigerant is thenalso resupplied to the first compressor, it is possible to store coolingenergy in the cascading heat exchanger or the second cooling circuit,when it is not required. The thermal energy found in the compressedfirst refrigerant can then be emitted to the cascading heat exchangeror, respectively, thermal energy can be deducted from the cascading heatexchanger in such a manner that a refrigerating capacity is stored inthe cascading heat exchanger. Instead of the heat exchanger, thecascading heat exchanger can consequently be cooled or supplied withrefrigerating capacity via the bridging bypass. If the first compressoris turned off, this refrigerating capacity can be guided back to thelow-pressure side by means of the first refrigerant via the way it came,thus enabling turning the first compressor off early.

If the first compressor is turned off, gaseous refrigerant on thelow-pressure side of the first cooling circuit in the flow directionupstream of the first compressor can be conducted in the cascading heatexchanger via the bypass, the first refrigerant being condensed in thecascading heat exchanger due to the refrigerating capacity or the lowthermal energy, respectively, stored there. A pressure on thelow-pressure side of the first cooling circuit drops due to thedecreasing density of the first refrigerant, which was increased becauseof the condensation. Since a condensation pressure in the bridgingbypass has changed only marginally after turning off the firstcompressor, a difference in pressure is still present in the bypassupstream of the heat exchanger, said difference in pressure being ableto be used for cooling the heat exchanger. It is essential to enableturning off the first compressor and possibly a fan on the condenserearly, a set temperature in the heat exchanger still being able to bemaintained or, respectively, a difference in temperature being able tobe compensated for a certain period of time. The unrequiredrefrigerating capacity generated by the first compressor can beintermediately stored in the cascading heat exchanger and be emittedagain by condensing the first refrigerant. Due to the thus decreasedoperating times of the first and the second compressor, the test chambercan be operated in a particularly energy-efficient manner.

An adjustable third expanding element can be arranged in the bypass and,in the first cooling circuit, liquid first refrigerant from ahigh-pressure side of the first cooling circuit can be expanded to agaseous first refrigerant by means of the third expanding element and beconducted to the low-pressure side via the heat exchanger. It thus alsobecomes possible to evaporate liquid first refrigerant from thehigh-pressure side via the third expanding element in such a manner thatthe first refrigerant is conducted into the heat exchanger, which iscooled thereby, in a renewed gaseous state through expansion due to adrop in pressure. The gaseous first refrigerant flowing out of the heatexchanger has a higher temperature level as a consequence of therefrigerating capacity emitted in the heat exchanger can be conducted tothe first compressor again. The bypass can basically be operatedindependently of an operation of the second cooling circuit or thesecond compressor, respectively. If the second cooling circuit of thesecond refrigerant is realized for a comparatively low temperaturelevel, it can also be intended to turn off the second compressor and tooperate or to also turn off the first compressor.

The second compressor can be stopped or turned off in a first step, thefirst compressor being able to be operated and condenses firstrefrigerant from a high-pressure side of the first cooling circuit beingable to be expanded to gaseous first refrigerant by means of the firstexpanding element when in the first cooling circuit and being able to beconducted to the low-pressure side via the cascading heat exchanger.Thus, a refrigerating capacity not required in the heat exchanger canstill be conducted from the high-pressure side of the first coolingcircuit to the cascading heat exchanger via the first expanding elementand be evaporated there, thermal energy of the cascading heat exchangerbeing able to be emitted to the first refrigerant. This leads to arefrigeration of the cascading heat exchanger, through which the secondrefrigerant no longer flows due to the second compressor being turnedoff.

Since, however, the second refrigerant is still in the cascading heatexchanger, thermal energy from the second refrigerant of the secondcooling circuit can be emitted to the first refrigerant of the firstcooling circuit and be stored in the cascading heat exchanger. Thesecond refrigerant can store refrigerating capacity by acting like akind of storage medium. Storing refrigerating capacity in the cascadingheat exchanger is particularly logical if little refrigerating capacityis required in the heat exchanger, which is simultaneously cooled by thebypass if necessary. Thermal energy is understood to be heat energy oralso heat content in Joule, a supply of heat increasing thermal energywhile dissipating heat prevents this. Thus, the cascading heat exchangercan also store thermal energy in such a manner that a refrigeratingcapacity can be stored by dissipating heat.

Subsequently, the first compressor can be turned off in a second step, adifference in pressure between the low-pressure side and thehigh-pressure side of the first cooling circuit being able to berealized in the cascading heat exchanger by condensing the firstrefrigerant to liquid first refrigerant. This presupposes that thecascading heat exchanger has been cooled enough or has stored so littlethermal energy that the gaseous first refrigerant can condense. For thispurpose, it can be intended for the cascading heat exchanger to havebeen cooled enough until a significant difference in temperature can beattained through cooling. By condensing the first refrigerant in thecascading heat exchanger and by realizing the difference in pressurebetween the low-pressure side and the high-pressure side of the firstcooling circuit, draining the first refrigerant via the bypass can beensured at least for so long as condensing the first refrigerant in thecascading heat exchanger is possible or the cascading heat exchanger hasnot been filled with liquid first refrigerant.

In the first cooling circuit, liquid first refrigerant from thehigh-pressure side of the first cooling circuit can be expanded togaseous first refrigerant by means of the third expanding element viathe difference in pressure and be conducted to the low-pressure side viathe heat exchanger. The cascading heat exchanger can be used as a kindof cold sink. By transferring thermal energy from the first refrigerantto the cascading heat exchanger, the second refrigerant or rather thestorage medium is reheated, the second refrigerant is evaporated and thefirst refrigerant is cooled, which leads to its condensation. Ifcondensing the first refrigerant in the cascading heat exchanger is notpossible due to a slight difference in temperature between the firstrefrigerant and the second refrigerant or if the cascading heatexchanger is filled with liquid first refrigerant, the first compressorcan be operated again. The first refrigerant can then change the flowdirection in the cascading heat exchanger and can evaporate again due toa difference in pressure set because of the operation of the compressorand be suctioned by the first compressor.

First refrigerant can be supplied to the low-pressure side via thefourth expanding element by means of an adjustable first internalsupplementary refrigeration line in the first cooling circuit, having asecond bypass, which is connected to a high-pressure side in the flowdirection upstream of the first expanding element and downstream of thecondenser and is connected to the low-pressure side in the flowdirection upstream of the first condenser and downstream of thecascading heat exchanger, and by means of an adjustable fourth expandingelement. Via the second bypass or the fourth expanding element,respectively, first refrigerant can be dosed such that a suction gastemperature and/or a suction gas pressure of the first refrigerant canbe adjusted on the low-pressure side of the first cooling circuitupstream of the first compressor. Through this, it can be preventedamong other things that the first compressor might overheat and thusbecomes damaged. By actuating the fourth expanding element, gaseousfirst refrigerant upstream of the first compressor can consequently becooled via the second bypass by adding still liquid first refrigerant indoses. The fourth expanding element can be actuated by an adjustingdevice, which itself is coupled to a pressure and/or temperature sensorin the first cooling circuit upstream of the first compressor. It isparticularly advantageous if a suction gas temperature of <30° C.,advantageously of <40° C., can be set via the second bypass. Firstrefrigerant can be conducted past the cascading heat exchanger via thesecond bypass in order to delay the first compressor from being turnedoff automatically or to prolong an operating period of the firstcompressor. Furthermore, it becomes possible to dynamically supply thecascading heat exchanger with first refrigerant or, depending on theloading condition at hand, to supply excess liquid first refrigerant,which is not required for cooling a suction gas temperature, to thecascading heat exchanger or the heat exchanger while operating the firstcompressor.

Furthermore, second refrigerant can be supplied to the low-pressure sidevia the fifth expanding element by means of an adjustable secondinternal supplementary refrigeration in the second cooling circuit,having a third bypass, which is connected to a high-pressure side in theflow direction upstream of the second expanding element and downstreamof the cascading heat exchanger and is connected to the low-pressureside in the flow direction upstream of the second compressor anddownstream of the heat exchanger, and by means of an adjustable fifthexpanding element. An improved operation, as has been described abovefor the first internal supplementary refrigeration, can also be attainedfor the second cooling circuit.

First refrigerant can be supplied to the low-pressure side via the sixthexpanding element by means of an adjustable first back-injection devicefor first refrigerant in the first cooling circuit, having a fourthbypass, which is connected to a high-pressure side in the flow directiondownstream of the first compressor and upstream of the condenser and isconnected to the low-pressure side in the flow direction upstream of thefirst compressor and downstream of the cascading heat exchanger, and bymeans of an adjustable sixth expanding element. After a recondensationof the first refrigerant in the cascading heat exchanger on thelow-pressure side, the first compressor must be put back into operationif the recondensation can no longer occur due to an increasingtemperature in the cascading heat exchanger. Due to the dropping vaporpressure, the first refrigerant evaporates in the cascading heatexchanger and a flow direction of the first refrigerant changes in thecascading heat exchanger. In this context, it would be disadvantageousif first refrigerant recondensed by the first compressor in thecascading heat exchanger is suctioned. This can be prevented by thefourth bypass or rather the first back-injection device realized thussupplying hot gaseous first refrigerant to the low-pressure sideupstream of the first compressor and thus promotes an evaporation of theliquid first refrigerant collected in the cascading heat exchanger.Nevertheless, it is possible to set a suction gas temperature and/or asuction gas pressure upstream of the first compressor via the firstback-injection device. The first back-injection device can form a socalled hot gas bypass.

Furthermore, second refrigerant can be supplied to the low-pressure sidevia the seventh expanding element by means of an adjustableback-injection device for second refrigerant in the second coolingcircuit, having a fifth bypass, which is connected to a high-pressureside in the flow direction downstream of the second compressor andupstream of the cascading heat exchanger and is connected to the lowpressure side in the flow direction upstream of the second compressorand downstream of the heat exchanger, and by means of an adjustableseventh expanding element. As described above for the first re-injectiondevice, the second cooling circuit can be operated advantageously.

It is particularly advantageous if a suction gas temperature and/or asuction gas pressure of the first and/or second refrigerant from thecorresponding low-pressure side of the cooling circuits can be adjustedupstream of the corresponding compressors, and/or that a difference inpressure can be compensated between the corresponding high-pressure sideand the corresponding low-pressure side of the cooling circuits. Amongother things, it can thus be prevented that the corresponding compressormight overheat and thus becomes damaged. It is particularly advantageousif a suction gas temperature of <30° C., advantageously of <40° C., canbe set. The corresponding refrigerant can also be dosed such that anoperating period of the corresponding compressor can be adjusted.Basically, it is disadvantageous if the compressor is often turned on oroff. A service life of a compressor can be prolonged if it is inoperation for longer periods at a time. Nevertheless, it is alsopossible to turn off the compressor for longer periods at a time.

The temperature control device can comprise a regulating device havingat least one pressure sensor and/or at least one temperature sensor inthe corresponding cooling circuits, magnetic valves of expandingelements being able to be actuated by means of the regulating device asa function of a measured temperature or pressure. The regulating devicecan comprise means for data processing which process data sets fromsensors and control the electrically controlled valves. Regulating afunctionality of the cascading cooling device can then also be adaptedto the correspondingly used refrigerant, for example via a correspondingcomputer program. Furthermore, the regulating device can signal amalfunction and cause the test chamber to be turned off, if necessary,in order to keep the test chamber or the test materials from beingdamaged by critical or undesired operating conditions of the testchamber.

If the expanding element is realized as a throttle having a electricallydriven valve, such as a magnetic valve, refrigerant can be dosed via thethrottle and the magnetic valve. The throttle can then be an adjustablevalve or a capillary, via which refrigerant can be conducted by means ofthe magnetic valve. The magnetic valve in turn can be actuated by meansof the regulating device.

A temperature ranging from −70° C. to +180° C. in temperature,preferably from −80° C. to +180° C., can be realized within the testchamber by means of the temperature control device. It is essential thata temperature ranging from >+60° C. to +180° C. in temperature can bereduced within the test space by means of the temperature controldevice. The corresponding refrigerants are heated considerably in theheat exchanger using the comparatively high temperature in the testspace, for which reason, from a technical point of view, a design of thefirst and the second cooling circuit can be adapted to a refrigerantheated to this temperature range at least on a low-pressure side of thecorresponding cooling circuit. A refrigerant heated thus can otherwiseno longer be ideally used on the high-pressure side of the correspondingcooling circuit.

The test chamber for conditioning a fluid, particularly air according tothe invention comprises a temperature-insulated test space sealableagainst an environment for receiving test materials and a temperaturecontrol device for controlling the temperature of the test space, atemperature ranging from −60° C. to +180° C. being able to be realizedwithin the test space by means of the temperature control device, saidtemperature control device comprising a cascading cooling device havinga first cooling circuit having a first refrigerant, a cascading heatexchanger, a first compressor, a condenser and a first expandingelement, and having a second cooling circuit having a secondrefrigerant, a heat exchanger arranged in the test space, a secondcompressor, the cascading heat exchanger and a second expanding element,said cascading heat exchanger being able to cooled by means of the firstcooling circuit, said first cooling circuit being realized having abypass passing through the heat exchanger and bridging the cascadingheat exchanger, said heat exchanger being able to be cooled by means ofthe first cooling circuit, and said temperature control devicecomprising a regulating device, by means of which the first compressorcan be turned off and the first refrigerant can be conducted andcondensed in the cascading heat exchanger on a low-pressure side of thebypass in a gaseous state.

The description of advantages of the method according to the inventionis referred to for deriving the advantages of the test chamber accordingto the invention. Overall, a thermal efficiency of the cascading coolingdevice can be increased, whereby a significant amount of energy can besaved. By not operating the first and the second compressor, the heatexchanger can be cooled for a comparatively longer period of time viathe bypass and the third expanding element respectively. Besides turningoff the first compressor, it is also possible to also turn off othercomponents of the cascading cooling device, such as a fan of thecondenser, or to turn off a water cooling in a water-cooled condenser.Furthermore, the cascading cooling device can be regulated moreprecisely using the turned off compressors since pressure andtemperature conditions in the first and second cooling circuit are notnegatively influenced by the compressors. The heat exchanger arranged inthe test space can also be arranged in an air treatment space of thetest space so that air circulated by a fan can come into contact withthe heat exchanger. It thus becomes possible to directly cool an amountof circulated air of the test space via the heat exchanger by means ofthe cascading cooling device.

Consequently, the first cooling circuit can be thermally coupled to thesecond cooling circuit by means of the cascading cooling device. Thefirst cooling circuit can then be a high-temperature cooling circuit andthe second cooling circuit can be a low-temperature cooling circuit. Inparticular, it can be intended to only use the second cooling circuit ifa temperature ranging from −70° C. to −20° C. in temperature is to berealized within the test space. Only using the first cooling circuit orrather turning off the second compressor becomes possible if atemperature of >−20° C. is to be realized within the test space.

The cascading heat exchanger can be formed by a plate heat exchangerwhose primary side can be connected to the first cooling circuit andwhose secondary side can be connected to the second cooling circuit. Thefirst refrigerant can then flow through the primary side and the secondrefrigerant can flow through the secondary side. If the secondcompressor is turned off, the second refrigerant is no longertransported on the secondary side and can serve as a storage medium. Forthis purpose, it can also be intended to provide the second coolingcircuit with suitable means which can compensate a rise or drop or inpressure by changing the density or the temperature of the storagemedium.

The bypass can be connected to a high-pressure side of the first coolingcircuit in a flow direction upstream of the first expanding element anddownstream of the first condenser and be connected to the low-pressureside of the first cooling circuit in a flow direction upstream of thefirst compressor and downstream of the cascading heat exchanger.

The temperature control device can comprise a heating device having aheater and a heating heat exchanger in the test space. The heatingdevice can be an electric resistance heater, for example, which heatsthe heating heat exchanger in such a manner that an increase intemperature in the test space is enabled via the heating heat exchanger.If the heat exchanger and the heating heat exchanger can be specificallycontrolled for cooling and heating the air, which is circulated in thetest space, by means of the regulating device, a temperature, whichranges in the previously indicated temperature range, can be realizedwithin the test space by means of the temperature control device. Inthis context, a temporal consistency in temperature of ±1 K, preferably<±0.3 K to ±0.5 K, can be realized during a test interval in the testspace independently of the test materials or rather an operatingcondition of the test materials. A test interval is understood to be atime segment of a complete test period in which the test materials areexposed to an essentially consistent temperature or climate condition.The heating heat exchanger can be combined with the heat exchanger ofthe first and second cooling circuit in such a manner that a sharedheat-exchanger body is formed through which the first and secondrefrigerant can flow and which comprises heating elements of andelectric resistance heater. The condenser of the first cooling circuitcan be realized having an air cooling or water cooling or a differentcooling liquid. Generally, the condenser can be cooled using anysuitable liquid. It is essential that the thermal load occurring at thecondenser is dissipated via the air cooling or water cooling in such amanner that the first refrigerant can condense such that it becomesfully liquefied.

BRIEF DESCRIPTION OF THE DRAWING FIGURE

In the following, a preferred embodiment of the invention is furtherdescribed with reference to the attached drawing.

The Figure illustrates a schematic view of a cascading cooling device 10having a first cooling circuit 11 and a second cooling circuit 12.Furthermore, the cascading cooling device 10 comprises a heat exchanger13 which is arranged in an indicated test space 14 and is connected tothe first cooling circuit 11 and the second cooling circuit 12.

DETAILED DESCRIPTION OF THE INVENTION

The first cooling circuit 11 is realized having a cascading heatexchanger 15, a first compressor 16, a condenser 17 and a firstexpanding element 18. In the first cooling circuit 11, a firstrefrigerant can be circulated by operating the first compressor 16. Thefirst expanding element 18 is made of a throttle 19 and a magnetic valve20. All other expanding elements of the cascading cooling device 10 canbe realized accordingly. The first cooling circuit 11 comprises ahigh-pressure side 21, which passes from the first compressor 16 to thefirst expanding element 18 in the flow direction of the firstrefrigerant, as well as a low-pressure side 22, which passes from thefirst expanding element 18 to the first compressor 16. The firstrefrigerant is gaseous and has a comparatively high temperature in atube section 23 extending from the first compressor 16 to the condenser17. The first refrigerant, which is compressed by the first compressor16, streams in the first cooling circuit 11 to the condenser 17, saidgaseous first refrigerant being liquefied in the condenser 17. Theexpanding element 18 comes after the condenser 17 in the first coolingcircuit 11 in the flow direction of the first refrigerant, said firstrefrigerant accordingly being available in a liquid state in a tubesection 24 of the first cooling circuit 11 between the condenser 17 andthe first expanding element 18. By expanding the first refrigerantdownstream of the first expanding element 18, the cascading coolingdevice 15 is cooled, the first refrigerant transitioning to the gaseousstate in a tube section 25 between the first expanding element 18 andthe cascading heat exchanger 15 and being conducted to the firstcompressor 16 via a tube section 26 of the cascading heat exchanger 15.

The second cooling circuit 12 comprises the heat exchanger 13, a secondcompressor 27, the cascading heat exchanger 15 and a second expandingelement 28 exchanger. The second cooling circuit 12 comprises ahigh-pressure side 29, which passes from the second compressor 27 to thesecond expanding element 28 in the flow direction of a secondrefrigerant, as well as a low-pressure side 30, which passes from thesecond expanding element 28 to the second compressor 27. Here as well,the second refrigerant is gaseous in a tube section 31 extending fromthe second compressor 27 to the cascading heat exchanger 15 and has acomparatively high temperature. The second refrigerant, which iscompressed by the second compressor 27, flows in the second coolingcircuit 12 to the cascading heat exchanger 15, said gaseous secondrefrigerant being liquefied in the cascading heat exchanger 15. In thesecond cooling circuit 12, the second expanding element 28 comes afterthe cascading heat exchanger 15 in the flow direction of the secondrefrigerant, said second refrigerant accordingly being available in theliquid state in a tube section 32 of the second cooling circuit 12between the cascading heat exchanger 15 and the second expanding element28. By expanding the second refrigerant downstream of the secondexpanding element 28, the heat exchanger 13 is cooled, said secondrefrigerant transitioning to the gaseous state in a tube section 33between the second expanding element 28 and the heat exchanger 13,particularly in the heat exchanger 13, and being conducted to the secondcompressor 27 from the heat exchanger 13 via a tube section 34.

In the first cooling circuit 11, a bypass 35 is formed which passesthrough the heat exchanger 13 and bridges the cascading heat exchanger15 of the cooling circuit 11. The bypass 35 is connected to thehigh-pressure side 21 in a flow direction upstream of the firstexpanding element 18 and downstream of the condenser 17 and is connectedto the low-pressure side 22 in a flow direction upstream of the firstcompressor 16 and downstream of the cascading heat exchanger 15.Furthermore, an adjustable third expanding element 36 is arranged in thebypass 35 in the flow direction upstream of the heat exchanger 13. Bymeans of the third expanding element 36, the first refrigerant can beexpanded and be conducted to the low-pressure side 22 via the heatexchanger 13. As long as no particularly low temperatures have to berealized in the heat exchanger 13, the second cooling circuit 12 can beturned off using the second compressor 27 so that the heat exchanger 13can be cooled via the bypass 35 of the first cooling circuit 11.

In this instance, the first expanding element 18 remains closed sincethe cascading heat exchanger 15 does not need to be cooled.

Nevertheless, the first refrigerant can be conducted from thehigh-pressure side 21 via the first expanding element 18 through thecascading heat exchanger 15 to the low-pressure side 22, if the secondcompressor 27 is stopped and the first compressor 16 is in operation,said cascading heat exchanger 15 or rather the second refrigeranttherein from the second cooling circuit then being cooled. Since thesecond refrigerant is not circulated, the cascading heat exchanger 15serves as a cold reservoir or rather thermal energy is emitted from thesecond refrigerant to the first refrigerant and thus a cold capacity isstored in the cascading heat exchanger 15. If, by means of the firstcooling circuit 11, a comparatively low cold capacity is to be yieldedin the heat exchanger 13 via the bypass or rather a difference intemperature to be compensated is comparatively slight, the firstcompressor 16 can be turned off also. The first refrigerant can thenflow in the cascading heat exchanger 15 and condense in the cascadingheat exchanger 15, a difference in pressure between the low-pressureside 22 and the high-pressure side 21 of the first cooling circuit 11being maintained owing to a thus realized change in density of therefrigerant. This leads to first refrigerant continuing to flow via thethird expanding element 36 and to the heat exchanger 13 being cooleduntil the first refrigerant can no longer be condensed in the cascadingheat exchanger 15 even when the first condenser 16 is turned off.Subsequently, the first compressor 16 can be operated again, a pressuredropping enough in the cascading heat exchanger 15 so that the liquefiedfirst refrigerant becomes gaseous again and thus is suctioned from thecascading heat exchanger 15. Overall, a significant amount of energy canthus be saved when operating the cascading cooling device 10.

Furthermore, an adjustable first internal supplementary refrigerationline is arranged in the first cooling circuit 11, said first internalsupplementary refrigeration 37 being realized having a second bypass 38,which is connected to the high-pressure side 21 in the flow directionupstream of the first expanding element 18 and downstream of thecondenser 17 and is connected to the low-pressure side 22 in the flowdirection upstream of the first compressor 16 and downstream of thecascading heat exchanger 15 having an adjustable fourth expandingelement 39. The first refrigerant can be supplied to the low-pressureside 22 via the fourth expanding element 39 so that the firstrefrigerant can lower a suction gas temperature upstream of the firstcompressor 16.

The second cooling circuit 12 also comprises an adjustable secondinternal supplementary refrigeration line 40 having a third bypass 41between the high-pressure side 29 and the low-pressure side 30 having afifth expanding element 42. In this instance as well, the secondrefrigerant can be cooled upstream of the second compressor 27 by meansof the second internal supplementary refrigeration 40 if required.

The first cooling circuit 11 further comprises an adjustable firstback-injection device 43 for the first refrigerant having a fourthbypass 44, which is connected to the high-pressure side 21 in the flowdirection downstream of the first compressor 16 and upstream of thecondenser 17 and is connected to the low-pressure side 22 in the flowdirection upstream of the first compressor 16 and downstream of thecascading heat exchanger 15. A sixth expanding element 45 is arranged inthe fourth bypass 44, hot and gaseous first refrigerant being able to besupplied from the high-pressure side 21 to the low-pressure side 22 bymeans of said sixth expanding element 45 whereby a suction gastemperature and/or a suction gas pressure of the first refrigerantbecoming adjustable on the low-pressure side 22 upstream of the firstcompressor 16. Moreover, a difference in pressure can be compensatedbetween the high-pressure side 21 and the low-pressure side 22.

The second cooling circuit 12 also comprises a second adjustableback-injection device 46 having a fifth bypass 47 and a seventhexpanding element 48, via which hot and gaseous second refrigerant canbe conducted from the high-pressure side 29 to the low-pressure side 30.

1. A test chamber for conditioning a fluid, particularly air, comprisinga temperature-insulated test space (14), which is sealable against anenvironment, for receiving test materials and a temperature controldevice for controlling the temperature of the test space, a temperatureranging from −60° C. to +180° C. in temperature being able to berealized within the test space by means of the temperature controldevice, said temperature control device having a cascading coolingdevice (10) having a first cooling circuit (11) having a firstrefrigerant, a cascading heat exchanger (15), a first compressor (16), acondenser (17) and a first expanding element (18), and having a secondcooling circuit (12) having a second refrigerant, a heat exchanger (13)arranged in the test space, a second compressor (27), the cascading heatexchanger and a second expanding element (28), said cascading heatexchanger being able to be cooled by means of the first cooling circuit,characterized in that the first cooling circuit is realized having abypass (35) passing through the heat exchanger and bridging thecascading heat exchanger, said heat exchanger being able to be cooled bymeans of the first cooling circuit, and said temperature control devicecomprising an adjusting device by means of which the first compressorcan be turned off and the first refrigerant being able to be conductedand condensed in a gaseous state in the cascading heat exchanger on alow-pressure side (22) of the bypass.
 2. The test chamber according toclaim 1, characterized in that the first cooling circuit (11) isthermally coupled to the second cooling circuit (12) by means of thecascading heat exchanger (15).
 3. The test chamber according to claim 1,characterized in that the cascading heat exchanger (15) is formed by aplate heat exchanger whose primary side is connected to the firstcooling circuit (11) and whose secondary side is connected to the secondcooling circuit (12).
 4. The test chamber according to claim 1,characterized in that the bypass (35) is connected to a high-pressureside (21) of the first cooling circuit (11) in a flow direction upstreamof the first expanding element (18) and downstream of the condenser (17)and to the low-pressure side (22) of the first cooling circuit in a flowdirection upstream of the first compressor (16) and downstream of thecascading heat exchanger (15).
 5. The test chamber according to claim 1,characterized in that the temperature control device comprises a heatingdevice having a heater and a heating heat exchanger in the test space(14).